Cosmetic material containing crystalline superfine silk powder

ABSTRACT

The invention provides a cosmetic material containing a crystalline superfine silk powder that has the original structure of silk yarn, properties such as an unique gloss, feeling of touch, flexibility, and elasticity; and various properties such as excellent coating power, spreadability, adhesion, feeling of touch, and formability, which are required of an extender powder or color material of cosmetics. The cosmetic material contains a colored crystalline superfine silk powder obtained by the steps of bringing a silk substance into contact with an alkali aqueous solution at temperatures ranging from 100° C. to 150° C. under a pressure ranging from 1 through 5 atmospheric pressures to weaken the silk substance to not greater than 0.02 g/d in tensile strength, dealkalizing and drying the silk substancepowdering the silk substance into a crystalline superfine silk powder below 3 μm in average particle diameter, and dyeing the crystalline superfine silk powder with a natural or synthetic color material, or mixing the crystalline superfine silk powder with a natural or synthetic color material.

TECHNICAL FIELD

The present invention relates to a cosmetic material that containscrystalline superfine silk powder below 3 μm in particle diameter and issuitable for application to the skin.

BACKGROUND TECHNOLOGY

Cosmetics include a variety of powders, for example, clay minerals (inthe field of cosmetics, powdered clay minerals are referred to as“extender pigments”) and/or color materials (for example, dyes andpigments).

Clay minerals include mainly talc, mica, kaolin, and sericite.

These powdered extender powders have been used for a long time becauseof their coating power, spreadability, adhesion, and the like, which arenecessary for cosmetic materials.

Moreover, the extender powder is contained in the powder cosmeticmaterial as a main ingredient. Taking talc as an example, which is atypical extender powder, it is contained in as high a proportion as 90%or more in talcum powder or baby powder, 80% in face rouge (compacttype), around 50 to 80% in the facial powder or solid-type facialpowder, and around 45% in eye shadow and cake-type foundations.Accordingly, the quality of the property of the extender powder becomesa decisive crucial factor in determining the quality of cosmetics.

Moreover, color materials for coloring cosmetic materials is dividedinto pigments and dyes: the pigment can be adsorbed by means of othersubstances whereas the dye can be adsorbed by means of other substances.

As a pigment, natural minerals such as tuff loam or loess, or powdercolor materials (inorganic pigments) of metallic oxides such as ironoxide, titanium oxide, zinc oxide, magnesium oxide, aluminum oxide,zirconium oxide, and chromium oxide have been conventionally used.

In the case of using cosmetics that contain these extender powders orcolor materials, particularly, a powder cosmetic material having a highcontent of an extender powder, complaints include drawbacks ofunsuitability to the skin due to the powdery property.

Such an attempt as to make the content of the extender powder as low aspossible to overcome this drawback would present a problem in that thefeeling of touch would be degraded and solidified substances wouldbecome readily breakable because of the lack of balance between thepowders.

Furthermore, the extender powder including talc, mica, kaolin, andsericite has coating power, spreadability, adhesion and the like to theskin surface. However, it absorbs moisture or lipids from the skin andcauses the skin to seize due to dehydration, lipid removal, drying orthe like. Its spreadability and adhesion cannot be said to besatisfactory.

On the other hand, coloring materials of natural minerals such as tuffloam or loess, and metallic oxide powders such as iron oxide, titaniumoxide, zinc oxide, magnesium oxide, aluminum oxide, zirconium oxide, andchromium oxide are useful as raw materials. However, they have nofunction of absorption and desorption of moisture, and no permeabilityof moisture, so that they cannot be said to be a material suitable forskin since they would prevent respiration of the skin when brought intointimate contact with the skin.

Moreover, the color of cosmetic materials is prepared with difficulty byone type of color material and thus several types of color materialshave been mixed for preparation.

In order to solve these extender powder or color material drawbacks, atechnique has been suggested for use in coating the surface of powderssuch as talc, kaolin, titanium oxide, zinc oxide or the like withreproduced fibroin that has excellent affinity to skin and is a materialsuitable for a living body with good absorption and desorption ofmoisture. (Refer to Japanese Patent Publication No. Sho 28-250, JapanesePatent Publication No. Sho 57-11577, Japanese Laid-Open PatentPublication No. Hei 9-25217, Japanese Laid-Open Patent Publication No.Hei 9-309816, and Japanese Laid-Open Patent Publication No. Hei9-302261).

In contrast to the development of a technique for such cosmetics whichemploys powders with color materials predominantly composed of anextender powder or a metallic oxide, which are predominantly composed ofthese clay minerals, coated with reproduced fibroin, research has beencarried out for a long time in attempts to use a silk substance singlyas a cosmetic powder.

For example, the invention according to Japanese Patent Publication No.Sho 26-4947 employs a silk powder as a cosmetic base material, the silkpowder being obtained by spraying a reproduced fibroin aqueous solutionin the atmosphere.

However, a reproduced silk powder, such as the silk powder according tothe aforementioned invention, which is obtained from an aqueous solutioninto which silk yarn is dissolved has low crystallinity, that is, thereproduced silk powder is an amorphous silk powder.

The amorphous silk is soluble in water. Accordingly, when such anamorphous silk powder is adhered to skin moist with perspiration, theamorphous silk powder absorbs the perspiration to partly dissolve andbecome viscous.

When this is touched by hand, the silk powder lumps (particles) tobecome rough to the touch and provides a bad appearance.

Skin moist with perspiration occurs daily, such as after playing sports,taking a bath, during the rainy season or in sultry summer weather. Incases where powder cosmetic materials are used under this skincondition, it can be naturally understood that powder cosmetic materialscontaining amorphous silk powder are not suitable.

Accordingly, amorphous silk powder can be used when it is in a liquidstate, that is, it can be used as a cosmetic material such as a lotionand can be used in a solid state (powder) with difficulty. In the caseof using amorphous silk as in a powder, its content is around 5% orless.

Thereafter, such a technique was developed as attempting to expand therange of applications of the silk powder as a cosmetic raw material byincreasing the crystallinity of the amorphous reproduced silk powder,that is, by decreasing the degree of solubility in water. An exampleincludes a fine reformed silk powder and the method for manufacturingthereof (Japanese Laid-Open Patent Publication No. Hei 4-337331), thefine reformed silk powder being provided with the crystallinity ofreproduced silk powder increased up to half that of silk yarn.

Other methods include one in which a silk powder obtained by powderingthe silk yarn mechanically or physically is used as a cosmetic rawmaterial.

For example, Japanese Patent Publication No. Sho 27-3650 provides a finesilk powder for use as a cosmetic material that is obtained throughtreatment of the silk yarn with an alkali aqueous solution,neutralization, washing in water, dehydration, drying, and powdering,with the diameter of the particles small enough to pass through a meshof No.300 (10 μm in particle diameter).

Moreover, a method is suggested in which the silk yarn is heated withsaturated vapor or heated vapor, then the silk is released to expandunder low pressure, and then dried to be powdered in order to obtain asilk powder 30 to 50 μm in diameter (refer to Japanese PatentPublication No. Sho 61-36840 and Japanese Patent Publication No. Sho63-51160). Another method is suggested in which the silk yarn isdissolved in a certain aqueous solution, then the aqueous solution isdialyzed to obtain a silk fibroin aqueous solution which is in turnbrought into contact with a coagulating liquid, and then theprecipitated fine particulate silk fibroin is dried to obtain a silkpowder of 6.5 to 19 μm in diameter (refer to Japanese Laid-Open PatentPublication No. Hei 4-88027). Another method is suggested in which thesilk fibroin is powdered in a multi-stage process where dry andmechanical powdering means are employed, and is subjected to β treatmentat least in one stage of the multi-stage process or after themulti-stage process to obtain a superfine silk fibroin powder 3.25 μm inaverage particle diameter. (Refer to Japanese Laid-Open PatentPublication No. Hei 6-339924.)

The present applicants have already suggested a method in which a silksubstance is brought into contact with an aqueous solution of an alkalimetal compound under an atmospheric pressure at a temperature of 95° C.or more to allow the substance to be weakened in strength, then theresulting silk substance is dealkalized and dried, and the silksubstance is powdered to obtain a crystalline superfine silk fibroinpowder 3 to 6 μm in average particle diameter (Japanese Laid-Open PatentPublication No. Hei 8-198970, Patent No. 2615440).

In the aforementioned prior arts, powders such as talc, kaolin, titaniumoxide, and zinc oxide, which are coated with the reproduced fibroin, canprovide a certain effect on solving these problems. However, their coresthemselves are made up of a metallic oxide and do not essentially makeimprovements in moisture and air permeability.

Moreover, the prior arts have a drawback in presenting a problem thatthe fibroin coating in use, which absorbs body fluids such as sweat, isstripped off from the metal oxide core and thus the surface of the metaloxide is apt to be exposed. Accordingly, they do not provide means foressentially solving the problems.

On the other hand, in the prior art that employs the silk powder as acosmetic raw material, such a silk powder has been developed as a coarsepowder several tens of μm in average particle diameter to a fine powder3 μm in average particle diameter.

However, powders around 10 μm in diameter or more lack the smoothfeeling of touch or the feeling of suitability. In addition, powdersbelow 10 μm and above 3 μm in diameter provide improved feelings oftouch and fitness, however, they are not yet satisfactory in this pointand still not sufficient in terms of formability (stability ofparticles).

The object of the present invention is to provide a cosmetic materialcontaining a crystalline superfine silk powder that is provided with theoriginal structure of silk yarn; with properties such as its uniquegloss, feeling of touch, flexibility, and elasticity; and with variousproperties such as excellent coating power, spreadability, adhesion,feeling of touch, and formability, which are required of the extenderpowder or color material of cosmetics.

Another object of the present invention is to provide a cosmeticmaterial in which part of or all of the extender powder or colormaterial which has been used in conventional cosmetics, is replaced bythe crystalline superfine silk powder that is provided with theaforementioned original structure of silk yarn; with properties such asits unique gloss, feeling of touch, flexibility, and elasticity; andwith various properties such as excellent coating power, spreadability,adhesion, feeling of touch, and dye-affinity by means of a pigment,which are required of the extender powder or color material ofcosmetics.

Another object of the present invention is to provide a cosmeticmaterial containing the coloring crystalline superfine silk powder thatis provided with functions as an extender powder or a color material.

DISCLOSURE OF THE INVENTION

In order to achieve the aforementioned objects, the present inventionemploys technical items as requirements as shown below.

That is, the present invention lies in:

(1) A cosmetic material containing a crystalline superfine silk powderobtained in the steps of bringing a silk substance into contact with analkali aqueous solution at a temperature of 100° C. or more under oneatmospheric pressure or more to weaken the silk substance in strength;thereafter, dealkalizing and drying the silk substance; and then,powdering the silk substance into powder below 3 μm in average particlediameter,

(2) A cosmetic material containing clay minerals and/or a colormaterial, wherein

part of or all of said clay mineral and/or a color material are replacedby a crystalline superfine silk powder obtained in the steps of bringinga silk substance into contact with an alkali aqueous solution at atemperature of 100° C. or more under one atmospheric pressure or more toweaken the silk substance in strength; thereafter, dealkalizing anddrying the silk substance; and then, powdering the silk substance intopowder below 3 μm in average particle diameter,

(3) A cosmetic material containing a crystalline superfine silk powderobtained in the steps of bringing a silk substance into contact with analkali aqueous solution at temperatures ranging from 100° C. to 150° C.under a pressure ranging from 1 through 5 atmospheric pressures toweaken the silk substance to not greater than 0.02 g/d in tensilestrength; thereafter, dealkalizing and drying the silk substance; andthen, powdering the silk substance into powder below 3 μm in averageparticle diameter,

(4) A cosmetic material according to aforementioned (1), (2), or (3),wherein when the silk substance is powdered, an impact powdering and africtional powdering are combined to powder the silk substance into acrystalline superfine silk powder below 3 μm in average particlediameter,

(5) A cosmetic material according to aforementioned (1), (2), (3), or(4), wherein when the silk substance is powdered, an impact powderingand a frictional powdering are combined to powder the silk substance,which is then classified into a crystalline superfine silk powder below3 μm in average particle diameter,

(6) A cosmetic material according to aforementioned (5), wherein whenpowdering is carried out by a combination of the impact powdering andthe frictional powdering, a dried silk substance is powdered into a silkpowder 4 to 15 μm in average particle diameter through the impactpowdering—the frictional powdering and the frictional powdering—theimpact powdering, or the frictional powdering—the impact powdering—thefrictional powdering being in sequence, and then the impact powdering iscarried out to obtain a crystalline superfine silk powder belw 3 μm inaverage particle diameter,

(7) A cosmetic material containing a colored crystalline superfine silkpowder obtianed by the steps of bringing a silk substance into contactwith an alkali aqueous solution at a temperature of 100° C. or moreunder one atmospheric pressure or more to weaken the silk substance instrength; thereafter, dealkalizing and drying the silk substance; then,powdering a resulting dried silk substance into a crystalline superfinesilk powder below 3 μm in average particle diameter; and thereafter,dyeing said crystalline superfine silk powder with a natural orsynthetic color material, or mixing said crystalline superfine silkpowder with a natural or synthetic color material,

(8) A cosmetic material containing clay minerals and/or a colormaterial, wherein

part of or all of said extender powder and/or a color material arereplaced by a colored crystalline superfine silk powder obtained in thesteps of bringing a silk substance into contact with an alkali aqueoussolution at a temperature of 100° C. or more under one atmosphericpressure or more to weaken the silk substance in strength; thereafter,dealkalizing and drying the silk substance; then, powdering the silksubstance into a crystalline superfine silk powder below 3 μm in averageparticle diameter; and thereafter, dyeing said crystalline superfinesilk powder with a natural or synthetic color material, or mixing saidcrystalline superfine silk powder with a natural or synthetic colormaterial,

(9) A cosmetic material containing a colored crystalline superfine silkpowder obtained by the steps of bringing a silk substance into contactwith an alkali aqueous solution at temperatures ranging from 100° C. to150° C. under a pressure ranging from 1 through 5 atmospheric pressuresto weaken the silk substance to not greater than 0.02 g/d in tensilestrength; thereafter, dealkalizing and drying the silk substance; then,powdering the silk substance into a crystalline superfine silk powderbelow 3 μm in average particle diameter; and thereafter, dyeing saidcrystalline superfine silk powder with a natural or synthetic colormaterial, or mixing said crystalline superfine silk powder with anatural or synthetic color material, and

(10) A cosmetic material containing a crystalline superfine silk powderobtained by the steps of bringing a silk substance into contact with analkali aqueous solution at temperatures ranging from 100° C. to 150° C.under a pressure ranging from 1 through 5 atmospheric pressures toweaken the silk substance to not greater than 0.02 g/d in tensilestrength; thereafter, dealkalizing and washing the silk substance inwater; then, dyeing the silk substance with a natural or synthetic colormaterial; and then, powdering the silk substance into a crystallinesuperfine silk powder below 3 μm in average particle diameter.

Production of Crystalline Superfine Silk Powder:

According to the present invention, in order to obtain crystallinesuperfine silk powder below 3 μm in average particle diameter, thefollowing configuration is employed. That is,

1) a raw material of a silk substance such as cocoon filaments, silkyarn, and raw silk

2) is brought into contact with an alkali aqueous solution,

3) at temperatures ranging from 100° C. to 150° C.,

4) under pressure ranging from 1 through 5 atmospheric pressures,

5) to weaken the silk substance to around 0.02 g/d or less in tensilestrength,

6) thereafter, the resulting silk substance is dealkalized and dried,and

7) then, the resulting dried silk substance is powdered.

In the present invention, it is important to treat the silk substance sothat the tensile strength thereof is reduced to around 0.02 g/d or less.It is difficult to obtain powder below 3 μm in average particle diameterwith a tensile strength above 0.02 g/d.

Moreover, it is important to treat the silk substance at a temperatureof 100° C. to 150° C. and under a pressure so as to provide uniformdegradation in strength.

Moreover, it is desirable to employ, in the powdering process, amulti-stage powdering method in two stages or more in which the impactpowdering and frictional powdering are combined together.

The silk substance for use in the present invention includes cocoonfilaments, raw silk, silk yarn (yarn from which sericin is excluded bydegumming), and lint such as leftover thereof.

Moreover, the silk substance can employ woven fabrics, knit fabrics,non-woven fabrics, net yarn, and the like, which are formed of theserespective yarns.

The silk substance can employ one or more selected from them.

In order to implement the present invention, the silk substance is firsttreated by being brought into contact with an alkali aqueous solution ata temperature above 100° C., preferably, at a temperature within a rangeof 120° C.±10° C. and under a pressure.

As an alkaline substance in the alkaline aqueous solution, sodiumcarbonate, sodium hydrogen-carbonate, potassium carbonate, sodiumhydroxide, potassium hydroxide may be used individually or mixed foruse.

The degree of alkalinity of the alkaline aqueous solution (alkalinity)is a pH of 9 to 12.5, preferably, a pH of 10.5 to 12.0.

With a pH of less than 9, the strength cannot be reduced uniformly andefficiently, while with a pH above 12.5, an excessive dissolved portionof the silk yarn or the like reduces the rate of collection.

Sodium carbonate, an alkaline substance, has a buffering action as anaqueous solution and an increase in concentration would hardly cause thepH thereof to increase up to the order of 12 or more.

However, a trace amount of mixture of sodium hydroxide into sodiumcarbonate may cause the total amount of alkaline substance used todecrease.

The silk substance in the alkali aqueous solution is treated by soakingthe silk substance in the alkaline aqueous solution of a temperatureabove 100° C.

The time for the silk substance to be in contact with the alkalineaqueous solution (alkali treatment time) is a time necessary to allowthe strength of the silk substance to uniformly decrease to a degreesuitable for forming a superfine powder regardless of whether it isdomestic silk or wild silk.

For example, a silk substance is kept in contact with the alkalineaqueous solution until the tensile strength thereof becomes around 0.02g/d or less and more preferably, up to such an extent that the strengthof the silk yarn is substantially immeasurable in the tensile test (0.01g/d or less), that is, until the silk yarn loses a form thereofavailable for measurement.

In general, the treatment time is 0.5 to 5 hours. In cases where silkyarn has yarn fabrics large in diameter or has sericin adhesion foundthereon or in cases where the strength cannot be readily decreased suchas in the case of wild silk yarn, two to three hours or more need to beadded or the concentration of the alkaline substance needs to beincreased.

A specific time required for alkali treatment can be determined byexamining the relationship between the ease of powdering the silksubstance whose strength has been reduced through the alkali treatment,the time for contact with the alkali, and the temperature.

What is important to reducing the strength of the silk substance throughthe alkali treatment is to allow the strength of the silk substance todecrease uniformly.

In this case, what is particularly essential is that if the silksubstance to be subjected to the alkali treatment is well separated,powder below 3 μm in average particle diameter may be obtained even byboiling (under an atmospheric pressure) at a temperature around 100° C.of the alkali treatment. However, this case will result in a variationin strength and lead to a prolonged alkali treatment time, requiring agreater amount of alkaline substance and thus providing a ratio ofcollection significantly reduced.

Therefore, it is important to weaken variations in strength after thealkali treatment irrespective of the portions of the silk substance suchas cocoon filaments and silk yarn.

The present invention overcomes this problem by performing the alkalitreatment under a pressure above the atmospheric pressure.

A pressure above the atmospheric pressure can be obtained by putting thesilk substance, an alkali substance, and water into a sealed containerand then by increasing the temperature thereof to a temperature greaterthan the boiling temperature. The pressure ranges substantially from 1through 5 atmosphere. A pressure ranging from 1 through 3 atmospheresmay be preferably employed in practice particularly in industrialproduction.

For example, the alkali treatment for the silk substance would becarried out more uniformly under a pressure of 0.01 atmosphere added toatmospheric pressure than under atmospheric pressure and provide a fineraverage particle diameter. However, it is far more effective topreferably carry out the alkali treatment under more than 0.1 atmosphereadded to the atmospheric pressure and more preferably under twoatmospheres, at a temperature of 120° C.±10° C.

The silk substance after having been subjected to the alkali treatmentis separated from the alkaline aqueous solution, thereafter alkalinesubstances adhered thereto are removed by washing in water to bedealkalized, and then the silk substance is dried.

Neutralization (pH7±1) or making the silk substance slightly acidic(pH5±1) with acids such as hydrochloric acid or tartaric acid will beeffective for the dealkalization.

Moreover, the addition of natural acids (such as a liquid squeezed outof a citrus, for example, lemon) after neutralization and washing inwater would allow the silk substance to effectively suit the skin andthus would make the substance more suitable for a powder raw materialfor use in cosmetics.

Drying is preferably carried out using a dryer for positive drying,however, natural drying should be also possible.

Subsequently, the powdering of the resulting silk substance is carriedout.

The superfine powdering of the silk substance is carried out by means ofcombining an impact powdering (coarse powdering and superfine powdering)with frictional powdering (grinding).

For example, any of the multi-stage powdering methods in a) through c)below are employed.

a) impact powdering (coarse powdering)→grinding→impact powdering(superfine powdering)→(particle size classification)

b) grinding→impact powdering (coarse powdering)→impact powdering(superfine powdering)→(particle size classification)

c) grinding→impact powdering (coarse powdering)→grinding→impactpowdering (superfine powdering)→(particle size classification)

Particles are preferably powdered into 4 to 15 μm in average particlediameter before the last impact powdering (superfine powdering) iscarried out.

In the end, crystalline silk superfine powdered particles below 3 μm inaverage particle diameter are obtained by the superfine powdering.

Within this range of particle diameter, impact powdering (superfinepowdering) is carried out with great efficiency.

In particular, powder below approximately 1 μm or less can be obtainedby the classification of particle sizes of the resultant silk superfinepowdered particles.

Furthermore, in order to obtain colored crystalline superfine silkpowder, one of the methods can be selectively used: one for powderingafter the silk substance having been subjected to the alkali treatmenthas been dyed with a natural or synthetic color material (such as anatural pigment, a synthetic pigment, a natural dye, or a syntheticdye); and the other for dyeing after powdering.

Pigments and dyes are apt to be fixed in an acid bath and thereforedyeing (after or before powdering the silk substance) with pigments ordyes is preferably carried out in an acid bath.

The resulting white or colored superfine silk powder provides anexcellent sense of touch.

In addition, the superfine silk powder has the power of solidificationand thus can be effectively used as a binder to increase the formabilityof a cosmetic raw material that has bad formability.

In particular, powder having a diameter of around 1 μm providessignificantly improved adhesion to the skin and spreadability and servesas a skin protective material including raw materials for cosmetics andresin composites.

In cases where the material silk substance is brought into contact withthe alkali aqueous solution to be treated under a pressure at atemperature of 100° C. to 150° C., the treatment is carried out bysoaking the silk substance into an alkaline aqueous solution in a glasscontainer or in a pressure-resistant metallic container made ofstainless steel.

At this time, in order to weaken the strength of the material silksubstance uniformly, fiber-shaped silk substances such as cocoonfilaments, raw silk, or silk yarn are preferably separated as much aspossible.

Dealkalization after the alkali treatment is carried out by repeatingwashing and dehydrating for neutralization of pH, or by neutralization(pH7±1) or making the silk substance slightly acidic (pH5±1) with acidssuch as hydrochloric acid or tartaric acid, and thereafter washing isrepeated through washing in water and a dehydration process.

In the dehydration process, a cloth-shaped filter, for example, a filterwith mesh so fine as to collect fine silk particles around 0.5 μm inparticle diameter is used.

In the alkali treatment process, non-crystalline portions of thematerial silk substance dissolve gradually into the alkali aqueoussolution and the dissolved silk substance is removed with water at thetime of dehydration. Accordingly, the silk substance to be powdered iscomprised of a crystalline silk substance in which the structureprovided intrinsically for silk yarn remains (crystalline structure of aβ-type with fibroin molecules uniaxially oriented).

In the alkali treatment under a pressure according to the presentinvention, the amount of an alkaline substance required is much lessthan that required in the case of the aforementioned U.S. Pat. No.2,615,440 in which the alkali treatment is carried out under a normalpressure. For example, the ratio of silk to carbonic acid soda must be1:1 in the case of Pat. No. 2,615,440, while the ratio of silk tocarbonic acid soda is only 1:0.5 in the case of the present invention inwhich the alkali treatment is carried out under a pressure at atemperature of 120° C.

This means that an improved effect is provided, in industrial productionof crystalline superfine silk powder, in which the number of times ofwashing in water and dehydration after the alkali treatment and theamount of acid required can be naturally reduced.

The silk substance has a property increasing the moisture absorption andwater absorption while decreasing the crystallinity, and the silkbecomes softened by absorbing moisture or water and is readily deformed.

When dried after the absorption of moisture or water, silk powder havingsuch low crystallinity flocculates firmly into hard clusters becominguseless. Accordingly, the powder needs to be a crystalline powder inorder to keep the unique property of silk. Therefore, it is desirable toemploy a physical powdering method for producing the crystalline powderin industry.

On the other hand, as described above, the prior arts were limited toobtain powder on the order of 3 μm in average particle diameter even byapplying physical powdering methods.

That is, any type of physical pulverizer provides powdered particles ofa limited size that is determined by the property of the poweredmaterial so long as the same type of pulverizer is used. Thus, powderlimitlessly small in diameter cannot be obtained.

In general, a pulverizer that provides a higher impact speed can producepowder of smaller diameters. However, the smaller the diameter of thepowder particles, the lower the particle's kinetic energy becomes. Thisdecreases the probability of exceeding the break speed of the particlesat which stress is produced sufficient to break the particles.Accordingly, the energy efficiency of the pulverizer will decrease in anaccelerated manner when the particles become smaller in diameter than acertain diameter.

Therefore, the average particle diameter that can be obtained by theconventional method, in which the silk substance is powdered to providesuperfine powder, is considered to be limited to 3 μm.

The powdering method is largely divided into two methods: one fordissolving and thereafter solidifying the silk substance to be powdered;the other for physically powdering the silk substance.

In the case where the silk substance is dissolved and thereafterpowdered, the structure provided intrinsically for silk does not remain(an uniaxially oriented β-type crystalline structure).

On the other hand, in the case where the silk yarn is physicallypowdered to form superfine silk powder, the structure providedintrinsically for silk yarn is left as it is, however, the amount of thestructure to remain depends on the powdering method, which exerts aneffect on the formability.

Manufacturing examples of crystalline superfine silk powder according tothe present invention are shown below.

MANUFACTURING EXAMPLE 1

An Eri silkworm cocoon shell is boiled in a 0.5% sodium carbonateaqueous solution (bath ratio of 50 times) to remove sericin, and is thenwashed in water and dried to form Eri silkworm silk yarn.

This silk yarn (fibroin fibers) with the composition shown in Table 1 isput into a stainless steel container and is treated for 2 hours at atemperature of 120° C. (under a pressure of 2.02 atmospheres) with thecontainer tightly closed.

Sodium hydrosulfite is a bleaching agent and Clewat is a trade name ofthe sequestering agent (made by The Teikoku Chemical Industry Co.,Ltd.).

These agents exert an effect on the whiteness of Eri silkworm yarn afterthe alkali treatment, which are required depending on the material ofthe container used and do not particularly exert an effect on thepowdering without using the agents.

The amount of sodium carbonate and the time of alkali treatment exert aneffect on the powdering.

In the case of Table 1, the strength of the silk substance was reducedto around 0.01 g/d.

The alkali treatment method is shown in Table 1.

TABLE 1 Eri silkworm silk yarn 20 (g) Sodium carbonate 8 (g)Seguestering agent (Clewat) 5 (g) Sodium hydrosulfite 1 (g) Water 600(g)

The tensile strength was measured by means of a Tensilon UTM-II.

An alkali solution containing alkali-treated Eri silkworm silk yarn wasreduced to 8.5 in pH with hydrochloric acid, then made slightly acidic(pH5±1) with tartaric acid, then put into a bag-shaped container ofwoven fabrics with a high degree of mesh, repeatedly washed in water anddehydrated four times, and then dried at around 40° C.

In the powdering treatment, an agitating crusher (a type by Ishikawa)was used for frictional powdering (or grinding) and then a rotary impactpulverizer (Sample Mill KI.-1 made by Fuji Denki Kogyo) was used forpowdering to obtain fine silk powder of around 12 μm in an averageparticle diameter.

Moreover, this fine powder is crushed by means of an air-jet pulverizer(Current Jet CJ-10 made by Nisshin Flour Milling Co., Ltd.) andthereafter classified by means of a classifier (Turbo classifier TC-16Nmade by Nisshin Flour Milling Co., Ltd.). Thus, superfine powder wasobtained which has average particle diameters of around 2.6 μm and 0.9μm (FIG. 1).

As can be seen clearly in FIG. 1, particles 5 μm or more in diameter arecontained among particles around 1 μm or less in an average particlediameter that are obtained through the powdering and classificationprocesses.

This superfine powder can be combined into fabrics around 10 μm in fiberdiameter to improve the property of the fabrics.

MANUFACTURING EXAMPLE 2

Bourette (by-product silkworm silk yarn not more than several twos of cmin the fiber length of the domestic silkworm yarn) produced in the silkspinning process was used as a raw material of the silk substance. Withthe composition shown in Table 2, the bourette was put into a glassbottle and treated for two hours at a temperature of 125° C. (under apressure of 2.37 atmosphere) with the bottle tightly sealed.

TABLE 2 Domestic silkworm silk yarn 20 (g) Sodium carbonate 4.5 (g)Clewat 4 (g) Sodium hydrosulfite 2 (g) Water 400 (g)

The treated silk substance was neutralized, washed in water, and dried,and thereafter powdered.

The substance was neutralized with hydrochloric acid to have a pH of7±1, and then dehydrated and washed in water repeatedly four times, andfinally dried at a temperature of 40° C.

The powdering treatment was carried out by means of the same pulverizerused in Manufacturing Example 1.

That is, in the powdering, the agitating crusher (a type by Ishikawa)was used for frictional powdering; then the rotary impact pulverizer(Sample Mill KI.-1 made by Fuji Denki Kogyo) was used for powdering; andthen the agitating crusher (a type by Ishikawa) was used again forfrictional powdering to obtain fine silk powder of around 11 μm in anaverage particle diameter.

This fine powder was crushed by means of the air-jet pulverizer (CurrentJet CJ-10 made by Nisshin Flour Milling Co., Ltd.) to obtain powder ofaround 2.0 μm in an average particle diameter after the air-jetsuperfine powdering treatment.

The powder was classified thereafter to obtain crystalline superfinesilk powder which has average particle diameters of around 2.5 μm and0.9 μm.

FIG. 2 shows the powdering process by a flow diagram.

MANUFACTURING EXAMPLE 3

Raw silk of domestic silkworms was boiled for one hour for degumming ina 0.1% sodium carbonate aqueous solution 50 times greater in quantitythan the raw silk to form fibroin fabrics (silk yarn).

This silk yarn was used as a material substance to perform an alkalitreatment under the conditions shown in Table 3.

For the powdering process after the alkali treatment, case (1), case(2), and case (3) of Table 3 were carried out like in the processesshown in FIG. 2 excluding the classifying process; case (4) of Table 3was carried out as in the process shown in FIG. 3; and case (5) of Table3 as in the process shown in FIG. 4.

FIG. 3 and FIG. 4 show flow diagrams of the powdering process.

Table 3 shows the average particle diameter of the resultant powder andthe ratio of powder collection.

In addition, classification of the resultant powder obtained in case (3)of Table 3 provided powder of 1.2 μm and 2.5 μm in an average particlediameter.

TABLE 3 Condition (1) (2) (3) (4) (5) Treatment temperature 100 110 120120 120 (° C.) Atmospheric pressure 1.03 1.46 2.02 2.02 2.02 (atm)Treatment time (h) 8 5 2.5 2.5 2.5 Sodium carbonate (g) 20 10 4 4 4Domestic silkworm silk 20 20 20 20 20 yarn (g) Sodium hydrosulfite (g) 11 1 1 1 Water (g) 500 500 500 500 500 Average particle 2.8 2.1 1.8 2.33.2 diameter (μm) Ratio of powder 50 55 60 60 60 collection (%)

REFERENCE TEST EXAMPLE 1

Table 4 shows the relationship between the average particle diameter ofthe silk powder particles and the adhesion property thereof, concerningthe silk powder of domestic silkworms which was obtained by the methodsof Manufacturing Examples 2 and 3, and in the intermittent processesthereof.

An amount of around 10 g of silk powder with different average particlediameters is placed on a sheet of paper and is spread to about 50 cm².Then, a test piece is placed on the powder to be adhered thereto andfurther, the test piece was covered with an amount of 10 g of the powderof the same average particle diameters.

Subsequently, the test piece buried in the powder was lifted verticallywith tweezers. Then, the test piece was weighed with the powder adheredthereto to calculate the amount of powder adhered to the surface andreverse side of the test piece per unit area.

The measurement was carried out in a room at a temperature of 20° C.with 65% RH.

The test piece had the shape of a film with a side thereof having anarea of around 10 cm² (10 cm²±0.5 cm²).

Three types of materials of metal (aluminum), resin (polyethylene), andnatural substance (silk fibroin) were used in the test piece.

As can be seen clearly in Table 4, over a range of average particlediameters around 3 μm or less, the smaller the particles diameter, thelarger the amount of powder adhered to the test piece for any material.

TABLE 4 Relationship between average particle diameter and adhesionproperty of silk powder particles Amount of powder adhered to Averageparticle the test piece (mg/cm²) diameter (μm) Silk fibroin PolyethyleneAluminum 0.9 3.003 0.863 1.418 1.21 2.887 0.761 1.233 2.32 1.390 0.5891.045 2.57 1.148 0.520 0.904 3.65 0.613 0.311 0.566 5.40 0.452 0.2970.491 12.20 0.304 0.206 0.281

REFERENCE TEST EXAMPLE 2

Using the silk powder obtained by the methods of Manufacturing Examples1 through 3, the sense of touch thereof was evaluated in a panelexperiment by five adult women.

The test was carried out in a room of constant temperature and constanthumidity at 20° C. with 65% RH. An amount of 1 g of silk powder wasplaced on the inside of the forearm of one arm and was pressed with theother hand to be rubbed in various directions. The subjects were askedto fill in a questionnaire of how they felt at that time.

The results are shown in Table 5.

As shown in Table 5, it can be seen that improved adhesion to the skin,spreadability, and smoothness are provided by the silk powder below 3 μmin an average particle diameter, particularly by that below 1 μm indiameter.

TABLE 5 Particle diameter (μm) Sense of touch 12 Rough feeling 8 Notrough to touch 5 Soft to touch 3.7 Soft to touch 2.3 Very soft to touch,good in adhesion to the skin, and good in spreadability on the skin 0.9Very soft to touch, very good in adhesion to the skin, and very good inspreadability on the skin

On the Manufacturing of Colored Crystalline Superfine Silk Powder

The crystalline superfine silk powder is colored and used as cosmeticmaterials. Here, the manufacturing of this colored crystalline superfinesilk powder is described below.

The crystalline superfine silk powder, according to the presentinvention, has a good dyeing property and is dyed with synthetic colormaterials such as natural pigments, synthetic pigments, natural dyes,synthetic dyes (such as direct dyes, acid dyes, basic pigments, andreactive dyes), or mixed with these color materials. The crystallinesuperfine silk powder is thereby dyed or colored into a variety ofcolors to be used as colored crystalline superfine silk powder.

In particular, the crystalline superfine silk powder is an extremelygood cosmetic raw material that can be dyed throughout said powder evenwith pigments.

This colored crystalline superfine silk powder also functions as anextender powder and a color material. Accordingly, when so colored as tohave a desired color, the powder requires no other pigments such ascolor materials and thus serves as a very useful cosmetic raw material.

Color materials for coloring include known color materials that areconventionally used for dyeing silk as a matter of course, as well asplant color materials such as curcuma, jasmine, carthamus, phellodendronamurense, madder, or paprika, a color material such as cochineal that isextracted from insects, and a color material such as shell purple thatcan be extracted from shells.

The color materials further include a color material extracted fromcolor cocoons such as domestic yellow cocoons, blue white cocoons, redcocoons, and bamboo-leaf-color cocoons. The green or blue of wildsilkworm cocoons and rhodinia fugax silkworm cocoons and the gold colorof cricula silkworm cocoons can also be used as a color material.

Manufacturing of Cosmetic Materials:

The crystalline superfine silk powder, according to the presentinvention, is a crystalline superfine silk powder, below 3 μm in anaverage particle diameter, that is provided with the original structureof silk yarn; with properties such as a unique gloss, feeling of touch,flexibility, and elasticity; and with various properties such as goodcoating power, spreadability, adhesion, feeling of touch, andformability, which are required of cosmetics.

Therefore, in a conventional cosmetic material containing an extenderpowder and/or a color material such as talc, mica, kaolin, or sericite,part of or all of the extender powder and/or color material can bereplaced with the aforementioned crystalline superfine silk powder below3 μm in an average particle diameter according to the present invention.

The cosmetic materials, according to the present invention, includethose predominantly composed of the aforementioned crystalline superfinesilk powder below 3 μm in an average particle diameter, morespecifically, such powdery cosmetics like facial powder or solid-typefacial powder, and face rouge composed of an oil agent (bonding agent)or a color material, eye shadows, and foundations (such as a cake typefoundation, a powdery foundation, an oil foundation, a stick foundation,and a liquid foundation).

The ratio of mixture of the crystalline superfine silk powder in acosmetic material (by weight) is 1 to 100% in a powdery material,preferably, 40 to 100%.

A cosmetic material like a lipstick composed of an oil agent (binder)has ratios from 1 to 70%, preferably, 1 to 40%.

A stick-shaped cosmetic material like a lipstick exceeding the ratio of70% is easily broken.

As described above, according to the present invention, the crystallinesuperfine silk powder below 3 μm in an average particle diameter iscontained in a cosmetic material to form a cosmetic raw material that isprovided with the original structure of silk (an uniaxially orientedβ-type crystalline structure); with properties such as an unique gloss,feeling of touch, flexibility, and elasticity; and with variousproperties such as good coating power, spreadability, adhesion, feelingof touch, and formability, which are required of an extender powder ofcosmetic materials.

Furthermore, said crystalline superfine silk powder can be colored witha variety of color materials into various colors, and serves as a colormaterial as well.

In particular, the crystalline superfine silk powder can be dyedthroughout with pigments, providing clear colors.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing a distribution of particle sizes of superfinepowder about 0.9 μm in an average particle diameter in ManufacturingExample 1.

FIG. 2 is a flow diagram showing a powdering process after an alkalitreatment.

FIG. 3 is a flow diagram showing a powdering process after an alkalitreatment.

FIG. 4 is a flow diagram showing a powdering process after an alkalitreatment.

FIG. 5 is a view showing a rupture test of a supporting beam employingpowder as a raw material.

FIG. 6 is a photograph showing the formability of formations obtainedfrom respective powders (talc, mica, titanium, and silk).

FIG. 7 is view showing the relationship between the size of acrystalline silk powder particle (average particle diameter) and MMD.

FIG. 8 is a graph showing the curves of reflectance, over wavelengths of360 through 700 nm, of (1) crystalline superfine silk powder (white),(2) Red No. 202, (3) crystalline superfine silk powder dyed with Red No.202, and (4) colored crystalline superfine silk powder with 50% of (1)and 50% of (3).

FIG. 9 is a graph showing the curve of reflectance, over wavelengths of360 through 700 nm, of crystalline superfine silk powder dyed under thecondition of Table 14 in Example 7.

BEST MODE FOR CARRYING OUT THE INVENTION

The embodiments of the present invention have been described above. Now,the examples (1 through 7) are to be shown below.

Moreover, the present invention is not limited to only the followingexamples.

EXAMPLE 1

A patch test for crystalline superfine silk powder and talc powder (skinirritation)

Talc JA-46R was used as the talc powder.

The crystalline superfine silk powder obtained in Manufacturing Example1 was used as the silk powder.

Test: With the silk and talc powder employed as specimens, theFinn-chamber was used for 20 adults (10 males and 10 females) ages 24through 59 to affix a silk powder and talc powder to the inside portionof the arm. The skin reaction was checked after 48 hours and 72 hours inaccordance with the criteria (based on “20 diagnostic clinicalimmunities of contact dermatitis by Shoujirou Nakagawa).

At 48 hours and 72 hours after the affixing, the affixed portion wasjudged by the naked eye with the results of the degree or irritation asshown in Table 6. The results were scored. The sum of the scores of therespective specimens was divided by the number of subjects andmultiplied by 100 to determine the irritation factors, which are shownin Table 7.

TABLE 6 Judgement on irritation and score of patch test Irritationjudgement Score No reaction: (−) 0 Trace of red spots: (±) 0.5 Clear redspots: (+) 1.0 Red spots and edema or invasion: (++) 2.0

TABLE 7 Irritation factor in patch test for silk and talc powder After48 hours After 72 hours Silk powder 0 0 Talc powder 10 15

EXAMPLE 2

The crystalline superfine silk powder of Example 1 was used to check theskin irritation of a lipstick.

The lipstick was prepared with the ratio of ingredients shown in Table8.

TABLE 8 Lipstick containing crystalline superfine silk powderCrystalline superfine silk powder 20 (%) Bees wax 5 (%) Candelabra wax 9(%) Carnauba wax 5 (%) Lanolin 11 (%) Castor oil 25 (%) 2-ethyl hexanoicacid cetyl 20 (%) Isopropyl myristic acid ester 4 (%) Glycyrrhiza 0.5(%) Tocopherol 0.5 (%)

For comparison, a lipstick A, made by maker A, which does not containsilk powder was used.

These lipsticks were used to carry out the same patch test as in Example1.

The patch test was carried out for 20 people of 14 males and 6 females,ages 26 through 63.

The test results are shown in Table 9.

It was found that the lipstick containing the crystalline superfine silkpowder had no skin irritation.

Lipstick A shows skin irritation, however, this is considered to be dueto the conventional extender powder contained therein.

TABLE 9 Irritation factor provided by patch test with lipstickcontaining crystalline superfine silk powder and lipstick A notcontaining silk made by maker A After 48 After 72 hours hours Lipstickcontaining crystalline superfine silk 0 0 powder Lipstick A 7.5 10

EXAMPLE 3

Formability of cosmetic powder and crystalline superfine silk powder

To examine the formability of powder, a comparative test was carried outbetween the crystalline superfine silk powder, and Talc (JA-46R), Mica(No.5500), Titan (A-100), and Kaolin (JP-100), which are used ascosmetic extender powders.

Silk yarn of Eri silkworms was used as a material of the crystallinesuperfine silk powder and was subjected to the same alkali treatment asin the Manufacturing Example 1 with the composition of Table 10.

The subsequent washing in water, drying, and powdering were carried outin the same manner as in Manufacturing Example 1. The resultant powderhad an average particle diameter of 1.7 μm.

The rupture strengths of support beams formed by the powders as rawmaterials were compared to each other in terms of formability.

In the test, as shown in FIG. 5, a beam was supported at an interval of4 cm and loaded at point A. The magnitude of the load provided at thetime of rupture was measured with Tensilon UTM-II (Toyo Baldwin Co.,Ltd.) as the rupture strength.

TABLE 10 Eri silkworm silk yarn 20 (g) Sodium carbonate 8.5 (g) Clewat 4(g) Hydrosulfite 2 (g) Water 400 (g)

The powders were formed by putting an amount of 2.0 g of each of thepowders into a mold of 10 mm (w)_(—)50 mm (L)_(—)30 mm (H) and beingsubjected to a load of 30 kg/cm².

FIG. 6 shows formations obtained from each powder. (The photographsshowing the formations of talc, mica, titanium, and silk.)

Each of the extender powders has a low formability and is broken in thecourse of taking the formation out of the mold. The titanium was readilybreakable in the direction of the load, while the mica was breakable inthe direction parallel to the load.

The kaolin and talc were breakable in both directions.

On the other hand, the crystalline superfine silk powder has goodformability and, as a result of the rupture test, was broken at 61.7 gof load.

Thereafter, an amount of 2.0 g of powder, into which 50wt % of silkpowder of Manufacturing Example 2 having 2.0 cm in an average particlediameter and 50 wt % of talc (JA-46R) were mixed, was put into the samemold as the above-mentioned and subjected to a load of 30 kg/cm² to beformed. The rupture load was measured to be 30.5 g.

The silk powder can also be used as a molding agent.

COMPARATIVE EXAMPLE 1

Formability of Amorphous Superfine Silk Powder

Raw silk of domestic silkworms was soaked into an aqueous solution 0.05%of carbon acid soda and boiled for 30 minutes with 50 times the bathratio of raw silk. After having been washed in water, the silk wasboiled again in an aqueous solution 0.05% of carbon acid soda (with 50times the bath ratio of raw silk), then washed in water, and dried.

The percentage of loss in boiling-off was 23.5%.

A liquid having a ratio of calcium chloride: ethyl alcohol: water=1:2:8(a mole ratio) was used as a dissolving liquid of silk yarn. The silkyarn from which sericin was removed as in the foregoing was dissolved inthe dissolving liquid ten times the silk yarn weight (g) at atemperature not more than 80° C.

In the dissolution, the dissolved matter was put into a cellophane tube(semi-transparent film) one hour after the dissolution of the silk yarnwas started (the silk yarn was dissolved almost completely in thistime), and then alcohol and salt were removed in pure water.

The resultant silk fibroin aqueous solution was freeze-dried.

The resultant silk fibroin was coarsely powdered by means of the rotaryimpact pulverizer (Sample Mill K-1 made by Fuji Denki Kogyo), and thenpowdered by means of air-jet pulverizer (Current Jet CJ-10 made byNisshin Flour Milling Co., Ltd.).

The resultant fine powder is a powder 3 through 5 μm in an averageparticle diameter and 85% of the powder in weight is amorphous fine silkpowder that shows solubility in water at room temperature (20° C.±10°C.). An amount of 2.0 g of this amorphous fine silk powder was put intoa mold with 10 mm (W)_(—)50 mm (L)_(—)30 mm (H) and subjected to a loadof 30 kg/cm² to be formed.

The formation was fragile and broken in a manner similar to that ofmica.

In the case where the rupture test is carried out in the method ofExample 3, the rupture test can be carried out with 1 through 4 g ofrupture strength.

However, it is difficult to carry out the rupture test with amorphousfine silk powder according to the method of Example 3. By consideringExample 4 as a reference, it was found that the amorphous fine silkpowder is worse in formability than crystalline superfine silk powder.

EXAMPLE 4

Particle Diameter and Formability of Silk Powder

To examine the formability of crystalline silk powder having differentparticle diameters, support beams made up of powder were subjected to arupture test.

First, by using bourette (domestic silkworm silk yarn) as a powdermaterial with the weight of the sodium carbonate of Table 11 beingvaried within the range from 2.5 through 4.5, the silk yarn wassubjected to the alkali treatment, washing in water, drying, andpowdering in the same manner as in Manufacturing Example 2.

The average particle diameters of the resultant silk powder were seventypes such as 1.2, 1.8, 2.4, 3.2, 5.4, 8.1, and 12.0 μm. These silkpowders were used as specimens in the test for formability.

An amount of 2.0 g of each powder was put into a mold with 10 mm(W)_(—)50 mm (L)_(—)30 mm (H) and subjected to loads of 1, 3, 30, 100,200, and 250 kg/cm² to be formed into beams.

TABLE 11 Bourette 20 (g) Sodium carbonate 2.5˜4.5 (g) Clewat 4 (g)Hydrosulfite 2 (g) Water 400 (g)

Subsequently, the test, as shown in FIG. 5, a beam was supported at aninterval of 4 cm and loaded at point A. A magnitude of the load providedat the time of rupture was measured with Tensilon UTM-II (Toyo BaldwinCo., Ltd.).

The results are shown in Table 12.

In terms of the feeling of touch and formability of powder, and thereleasing property of the formed powder, the range available for solidcosmetics lies in A, more preferably, in B in Table 12.

TABLE 12

COMPARATIVE EXAMPLE 2

Silk powder was manufactured according to the method for manufacturingsilk fibroin fine powder, which is described in Japanese Laid-OpenPatent Publication No. Hei 6-339924.

The average particle diameter was 5.2 μm.

An amount of 2.0 g of this sik powder was put into a mold of 10 mm(W)_(—)50 mm (L)_(—)30 mm (H) and subjected to a load of 100 kg/cm² tobe formed into a beam.

The magnitude of the rupture strength of the beam was measured withTensilon UTM-II as shown in FIG. 5, being found to be 9.4 g.

Based on the fact that the rupture strength of powder 5.4 μm in averageparticle diameter is 36.7 g at a load of kg/cm² in Table 12, the silkpowder of Comparative Example 2 is around a quarter the rupture strengthof the silk powder according to the present invention.

The crystalline superfine silk powder of the present invention preservesthe original structure of silk yarn. The various properties thereof suchas the surface structure, elasticity, and flexibility are notessentially different from those of silk yarn, so that the crystallinesuperfine silk powder has high formability.

On the other hand, the silk powder of Comparative Example 2 allows thepowder particles to turn into an amorphous state in the course of themanufacturing of crystallizing with an alcohol. However, since the silkpowder does not maintain the original structure of silk yarn, the silkpowder is considered to have low formability.

Silk powder particles having the original structure of silk yarn wouldshow the same birefringence as silk yarn, and observation of theparticles under a polarizing microscope using an inspection plate willshow particles in yellow or blue. In contrast, the amorphous powder thatis crystallized with alcohol shows no birefringence.

Appearance of birefringence in the non-crystalline powder would not showsuch a high value as that of silk yarn, so that observation by thecombination of the shape of the particles and birefringence wouldsubstantially show whether the structure provided intrinsically for silkremains in the powder.

Then, in the observation of the silk powder of Comparative Example 2described above under a polarizing microscope using an inspection plate,20 through 30% of the particles did not clearly show the samebirefringence as that of silk yarn even when the direction of theparticles were rotated.

In the case of the crystalline superfine silk powder of the presentinvention, the particles 1.2 μm in average particle diameter or more,clearly show the same birefringence as that of silk yarn.

Moreover, this powder including many smaller particles of not more than0.1 μm in diameter, would not show the same birefringence as that ofsilk yarn.

EXAMPLE 5

Diameter of Silk Powder Particles and Feeling of Friction

The feeling of friction of the crystalline superfine silk powderobtained by powdering silk yarn after the alkali treatment is shown withvariations in the mean frictional coefficient (MMD) obtained using theKES apparatus (KES-FB4, a surface property measuring apparatus) made byKato Tech. Co., Ltd.

The MMD relates to the feeling of roughness that one feels when one rubsthe surface of an object. The smaller the MMD, the smoother the surfaceof the object.

The crystalline superfine silk powder is the same as that of Example 4.

An amount of 8.0 g of each of the powders is put into an aluminum pan5.7 cm in inner diameter and is subjected to a pressure of 40 kg/cm², atwhich the releasing property of the formed powder is considered optimum.

For the application of pressure, a Mini press -10 made by Toyo SeikiCo., Ltd. was used.

For measurement of the MMD, the aforementioned aluminum pan was set onthe surface property measuring apparatus (KES-FB4).

The friction contact (50 g) in the portion to be brought into contactwith the surface of the press formed powder is piano wires of 0.5 mm indiameter, 5 mm in length, 10 pieces arranged in parallel to one another,with the contact area of 5 mm×5 mm.

The friction contact was drawn on the surface of the powder for adistance of 2 cm at a speed of 1 mm/sec in a direction perpendicular tothat of the piano wires to measure the frictional tension, while beingdrawn, with the surface property measuring apparatus. Then, the value ofMMD was calculated.

The calculated results are shown in FIG. 7.

The MMD suddenly increases with the increasing diameter of particles forthose not less than 3 μm in diameter.

On the other hand, as for the particle diameter and feeling of touch ofthe crystalline superfine silk powder, particles of not more than 6 μmin diameter provide a good feeling of touch, while those not more than 3μm in diameter provide a very good feeling of touch. Thus, inparticular, those below 3 μm in diameter are preferably used as cosmeticpowder.

EXAMPLE 6

Dyeing Property of the Crystalline Superfine Silk Powder

First, a dyeing bath of Table 13 was prepared.

The dyeing solution was red.

In the same manner as in Example 1, an amount of 20 g of the silksubstance obtained by allowing bourette to be treated with an alkali,wased in water, and dried was soaked in the dyeing bath of Table 13 forone hour at room temperature to be dyed red.

The dyeing solution was red at first and turned transparent one hourlater, most of the pigment of Red No. 202 (Tomomi Kasei Co., Ltd.) wasdyed to the silk substance.

The silk substance was dried and powdered in the same manner as inManufacturing Example 2 to obtain colored crystalline superfine silkpowder.

TABLE 13 Dyeing solution Water 1000 (g) Tartaric acid 1 (g) Red No.202 2(g)

The resultant dyed powder was 2.1 μm in average particle diameter.Colors were measured, by means of an automatic spectrophotometerUV-3100S, using (1) the white crystalline superfine silk powder obtainedin Manufacturing Example 2 (2.0 μm), (2) dye of Red No.202 (Tomomi KaseiCo., Ltd.), (3) powder dyed red obtained in Example 6 (2.1 μm), and (4)powder into which 50% of the white silk powder of Manufacturing Example2 and 50% of the red powder obtained by dyeing in Example 6 were mixed.

The color of each powder was determined based on the reflectance ofwavelengths ranging from 360 through 700 nm (FIG. 8).

Curves (3) and (4) for red have a valley between 500 and 550 nm, whilecurve (1) is a curve for white, which reflects most visible light.

Curve (4) is closer to curve (3) than the in-between curves (1) and (3).This colored crystalline superfine silk powder has excellent propertiesas a pigment.

Red No.202 (Tomomi Kasei Co., Ltd.) is a pigment and absorbs the silksubstance well.

An amount of 2.0 g of each of the powders (two powders, (3) and (4)) wasput into a mold of 10 mm (W)_(—)50 mm (L)_(—)30 mm (H) and subjected toa load of 40 kg/cm² to be press formed. The rupture strength (measuredby the same method as in Example 4) of the resultant formation wasmeasured to be in the range of 50 through 100 g.

EXAMPLE 7

Dyeing Property of Crystalline Superfine Silk Powder With a ColorMaterial of Color Cocoons

A color material was extracted from the yellow cocoon shell ofyellow-white cocoons of domestic cocoons to dye crystalline superfinesilk powder. An amount of 20 g of cocoon shells was soaked in anextracting solution of 400 g containing 80% of methyl alcohol and 20% ofwater (by weight) to extract a color material at a temperature of 65° C.for one hour.

On the other hand, an amount of 5 g of the crystalline superfine silkpowder of Manufacturing Example 2 was soaked in each of theaforementioned extracting solutions of 10, 20, 30, 40, 50, 60, and 70 g.Soaking was maintained for 10 hours at temperatures of 20 to 40° C. andthe powder was dried.

After having been dried, the powder was powdered by means of a rotaryimpact pulverizer (Sample Mill KI-1 made by Fuji Denki Kogyo), and thenpowdered by means of an air-jet pulverizer (Current Jet CJ-10 made byNisshin Flour Milling Co., Ltd.) into superfine powder.

The resultant crystalline fine silk powder was 2.1 μm±0.2 μm in anaverage particle diameter.

Colors of four points (Table 14) of the crystalline superfine silkpowder that had been dyed as described above were measured by means ofan automatic spectrophotometer UV-3100S.

The color of each of the dyed powders was determined based on thereflectance (FIG. 9) of wavelengths from 360 through 700 nm.

A patch test was carried out as in Example 1 using the crystallinesuperfine silk powder dyed as such.

As for results, no skin irritation was found in the 20 subjects.

An amount of 2.0 g of each of the powders (four points of Table 14) wasput into a mold of 10 mm (W)_(—)50 mm (L)_(—)30 mm (H) and subjected toa load of 40 kg/cm² to be press formed. The rupture strength (measuredby the same method as in Example 3) of the resultant formation wasmeasured to be found in the range of 50 to 100 g.

TABLE 14 Dyeing conditions of crystalline superfine silk powder with acolor material extracted from color cocoons Crystalline superfine silkColor material extracting powder (g) solution (g) 1 5 0 2 5 20 3 5 40 45 70

INDUSTRIAL APPLICABILITY

The present invention is applied to a cosmetic material that containscrystalline superfine silk powder below 3 μm in particle diameter and issuitable for the skin. It is also applicable to the field of medicine,as well as to the field of clothing from the common viewpoint of contactwith the skin.

What is claimed is:
 1. A cosmetic material containing a crystallinesuperfine silk powder obtained by the steps of: bringing a silksubstance into contact with an alkali aqueous solution at temperaturesranging from more than 100° C. to 150° C. and a pressure ranging frommore than 1 through 5 atmospheric pressures to reduce the tensilestrength of the silk substance to not greater than 0.02 g/d withoutdissolving the silk substance, dealkalizing and drying the silksubstance, and powdering the silk substance into a crystalline powderbelow 3 μm in average particle diameter.
 2. A cosmetic materialaccording to claim 1, wherein when the silk substance is powdered, animpact powdering and a frictional powdering are combined to powder thesilk substance into a crystalline superfine silk powder below 3 μm inaverage particle diameter.
 3. A cosmetic material according to claim 1,wherein when the silk subtance is powdered, an impact powdering and africtional powdering are combined to powder the silk substance, which isthen classified into a crystalline superfine silk powder below 3 μm inaverage particle diameter.
 4. A cosmetic material according to claim 2,wherein when powdering is carried out by a combination of the impactpowdering and the frictional powdering, the dried silk substance ispowdered into a silk powder 4 to 15 μm in average particle diameterthrough impact powdering—frictional powdering and fricitionalpowdering—impact powdering, or frictional powdering—impactpowdering—fricitonal powdering in sequence, and then impact powdering iscarried out to obtain a crystalline superfine silk powder below 3 μm inaverage particle diameter.
 5. A cosmetic material containing a coloredcrystalline superfine silk powder obtained by the steps of: bringing asilk substance into contact with an alkali aqueous solution at atemperature ranging from more than 100° C. to 150° C. and a pressureranging from more than 1 through 5 atmospheric pressures to reduce thetensile strength of the silk substance to not greater than 0.02 g/d,dealkalizing and drying the silk substance, powdering the silk substanceinto a crystalline superfine silk powder below 3 μm in average particlediameter, and either dyeing said crystalline superfine silk powder witha natural or synthetic coloring material or mixing said crystallinesuperfine silk powder with a natural or synthetic coloring material. 6.A cosmetic material containing a crystalline superfine silk powderobtained by the steps of: bringing a silk substance into contact with analkali aqueous solution at a temperature ranging from more than 100° C.to 150° C. and a pressure ranging from more than 1 through 5 atmosphericpressures to reduce the tensile strength of the silk substance to notgreater than 0.02 g/d, dealkalizing and washing the silk substance inwater, dyeing the silk substance with a natural or synthetic coloringmaterial, and powdering the silk substance into a crystalline superfinesilk powder below 3 μm in average particle diameter.
 7. A method ofpreparing crystalline superfine silk powder having an average particlediameter less than 3 μm, comprising the steps of: contacting a silksubstance with an alkali aqueous solution at a temperature of more than100° C. and a pressure of more than one atmosphere to reduce the tensilestrength of the silk substance to no greater than 0.02 g/d withoutdissolving the silk substance; dealkalizing the silk substance havingthe reduced tensile strength; drying the dealkalized silk substance; andpowdering the dried silk substance to obtain crystalline superfine silkpowder having an average particle diameter less than 3 μm.
 8. The methodof claim 7, wherein the tensile strength of the silk substance is nogreater than 0.01 g/d.
 9. A method of preparing a cosmetic materialcontaining a colored crystalline superfine silk powder having an averageparticle diameter less than 3 μm, comprising the steps of: contacting asilk substance with an alkali aqueous solution at a temperature of frommore than 100° C. to 150° C. and a pressure ranging from more than 1through 5 atmospheres to reduce the tensile strength of the silksubstance to no greater than 0.02 g/d; dealkalizing the silk substancehaving the reduced tensile strength; drying the dealkalized silksubstance; powdering the dried silk substance to obtain crystallinesuperfine silk powder having an average particle diameter less than 3μm; and either dyeing the crystalline superfine silk powder with anatural or synthetic coloring material or mixing the crystallinesuperfine silk powder with a natural or synthetic coloring material. 10.A method of preparing a cosmetic material containing a crystallinesuperfine silk powder having an average particle diameter less than 3μm, comprising the steps of: contacting a silk substance with an alkaliaqueous solution at a temperature of from more than 100° C. to 150° C.and a pressure ranging from more than 1 through 5 atmospheres to reducethe tensile strength of the silk substance to no greater than 0.02 g/d;dealkalizing and washing the silk substance in water; drying the silksubstance; dyeing the silk substance with a natural or syntheticcoloring material; and powdering the silk substance into a crystallinesuperfine silk powder having an average particle diameter than than 3μm.
 11. A cosmetic material containing a crystalline-superfine silkpowder obtained by the steps consisting essentially of: bringing a silksubstance into contact with an alkali aqueous solution at temperaturesranging from more than 100° C. to 150° C. and a pressure ranging frommore than 1 through 5 atmospheric pressures to reduce the tensilestrength of the silk substance to not greater than 0.02 g/d withoutdissolving the silk substance; dealkalizing and drying the silksubstance; and powdering the silk substance into a crystalline powderbelow 3 μm in average particle diameter.
 12. A method of preparingcrystalline superfine silk powder having an average particle diameterless than 3 μm, consisting essentially of the steps of: contacting asilk substance with an alkali aqueous solution at a temperature of morethan 100° C. and a pressure of more than one atmosphere to reduce thetensile strength of the silk substance to no greater than 0.02 g/dwithout dissolving the silk substance; dealkalizing the silk substancehaving the reduced tensile strength; drying the dealkalized silksubstance; and powdering the dried silk substance to obtain crystallinesuperfine silk powder having an average particle diameter less than 3μm.